306 research outputs found
Glass transition in fullerenes: mode-coupling theory predictions
We report idealized mode-coupling theory results for the glass transition of
ensembles of model fullerenes interacting via phenomenological two-body
potentials. Transition lines are found for C60, C70 and C96 in the
temperature-density plane. We argue that the observed glass-transition behavior
is indicative of kinetic arrest that is strongly driven by the inter-particle
attraction in addition to excluded-volume repulsion. In this respect, these
systems differ from most standard glass-forming liquids. They feature arrest
that occurs at lower densities and that is stronger than would be expected for
repulsion-dominated hard-sphere-like or Lennard-Jones-like systems. The
influence of attraction increases with increasing the number of carbon atoms
per molecule. However, unrealistically large fullerenes would be needed to
yield behavior reminiscent of recently investigated model colloids with strong
short-ranged attraction (glass-glass transitions and logarithmic decay of
time-correlation functions).Comment: 10 pages, 5 figure
Diagrammatic method for theory of magnetic and resistive properties of manganites
Effective field theory of magnetic and resistive properties of manganites
with account of strong Hund exchange coupling and electron-phonon interactions
has been evolved under the strong Hund coupling condition. In parallel with
Lang-Firsov unitary transformation of the zeroth Hamiltonian, we have realized
the diagonalization of Hund's Hamiltonian neglecting the upper triplet. The
diagram techniques taking into account the quantum spin fluctuations of lower
quintet and hole state with spin S=3/2 was developed. The magnetic structure of
the ground state and an influence of electron-phonon interaction have been
analyzed using the first nonvanishing approximation of perturbation theory. The
calculated temperature dependence of resistivity agrees well with experimental
data including these obtained in applied magnetic field.Comment: 44 pages, 14 figure
Existence theorems in the geometrically non-linear 6-parametric theory of elastic plates
In this paper we show the existence of global minimizers for the
geometrically exact, non-linear equations of elastic plates, in the framework
of the general 6-parametric shell theory. A characteristic feature of this
model for shells is the appearance of two independent kinematic fields: the
translation vector field and the rotation tensor field (representing in total 6
independent scalar kinematic variables). For isotropic plates, we prove the
existence theorem by applying the direct methods of the calculus of variations.
Then, we generalize our existence result to the case of anisotropic plates. We
also present a detailed comparison with a previously established Cosserat plate
model.Comment: 19 pages, 1 figur
Technical Note: Chemistry-climate model SOCOL: version 2.0 with improved transport and chemistry/microphysics schemes
International audienceWe describe version 2.0 of the chemistry-climate model (CCM) SOCOL. The new version includes fundamental changes of the transport scheme such as transporting all chemical species of the model individually and applying a family-based correction scheme for mass conservation for species of the nitrogen, chlorine and bromine groups, a revised transport scheme for ozone, furthermore more detailed halogen reaction and deposition schemes, and a new cirrus parameterisation in the tropical tropopause region. By means of these changes the model manages to overcome or considerably reduce deficiencies recently identified in SOCOL version 1.1 within the CCM Validation activity of SPARC (CCMVal). In particular, as a consequence of these changes, regional mass loss or accumulation artificially caused by the semi-Lagrangian transport scheme can be significantly reduced, leading to much more realistic distributions of the modelled chemical species, most notably of the halogens and ozone
Reliable Correlation for Liquid–Liquid Equilibria outside the Critical Region
A simple model for binary liquid–liquid equilibrium data correlation is explored. The model describes liquid–liquid equilibrium in terms of Henry’s law and unsymmetrically normalized activity coefficients in each phase. A procedure for parameter estimation including an approach to initial guesses, uncertainty analysis of regression results, obtained parameters, and predicted mole fractions has been formulated. The procedure is applied to three cases: hydrocarbons + water, ionic liquids + water, and nitroethane + hydrocarbons. The model has four parameters in the most basic formulation. Depending upon the available data, this number can be extended in a systematic fashion. We compare results of correlation to results obtained with a four-parameter nonrandom two-liquid (NRTL) equation and COSMO-SAC. In general, the new model does nearly as well as NRTL. Advantages of the presented model are a simple form and a parameter set that can be extended in a systematic fashion with an interpretation in terms of thermodynamic properties. The model may be developed further for validation of experimental data
Quantum phase transitions and thermodynamic properties in highly anisotropic magnets
The systems exhibiting quantum phase transitions (QPT) are investigated
within the Ising model in the transverse field and Heisenberg model with
easy-plane single-site anisotropy. Near QPT a correspondence between parameters
of these models and of quantum phi^4 model is established. A scaling analysis
is performed for the ground-state properties. The influence of the external
longitudinal magnetic field on the ground-state properties is investigated, and
the corresponding magnetic susceptibility is calculated. Finite-temperature
properties are considered with the use of the scaling analysis for the
effective classical model proposed by Sachdev. Analytical results for the
ordering temperature and temperature dependences of the magnetization and
energy gap are obtained in the case of a small ground-state moment. The forms
of dependences of observable quantities on the bare splitting (or magnetic
field) and renormalized splitting turn out to be different. A comparison with
numerical calculations and experimental data on systems demonstrating magnetic
and structural transitions (e.g., into singlet state) is performed.Comment: 46 pages, RevTeX, 6 figure
Характеризация наночастиц кристаллического кремния, легированного железом, и их модификация цитрат-анионами для использования in vivo
Objectives. This paper presents data on the development and study of the structural properties of iron-doped crystalline silicon (nc-Si/SiOx/Fe) nanoparticles obtained using the plasma-chemical method for application in magnetic resonance imaging diagnostics and treatment of oncological diseases. This work aimed to use a variety of analytical methods to study the structural properties of nc-Si/SiOx/Fe and their colloidal stabilization with citrate anions for in vivo applications.Methods. Silicon nanoparticles obtained via the plasma-chemical synthesis method were characterized by laser spark emission spectroscopy, atomic emission spectroscopy, Fouriertransform infrared spectroscopy, and X-ray photoelectron spectroscopy. The hydrodynamic diameter of the nanoparticles was estimated using dynamic light scattering. The toxicity of the nanoparticles was investigated using a colorimetric MTT test for the cell metabolic activity. Elemental iron with different Fe/Si atomic ratios was added to the feedstock during loading.Results. The particles were shown to have a large silicon core covered by a relatively thin layer of intermediate oxides (interface) and an amorphous oxide shell, which is silicon oxide with different oxidation states SiOx (0 ≤ x ≤ 2). The samples had an iron content of 0.8–1.8 at %. Colloidal solutions of the nanoparticles stabilized by citrate anions were obtained and characterized. According to the analysis of the cytotoxicity of the modified nanosilicon particles using monoclonal K562 human erythroleukemia cells, no toxicity was found for cells in culture at particle concentrations of up to 5 µg/mL.Conclusions. Since the obtained modified particles are nontoxic, they can be used in in vivo theranostic applications.Цели. В работе приводятся данные по разработке и изучению структурных свойств полученных плазмохимическим методом наночастиц кремния nc-Si/SiOx/Fe, легированных железом. Цель работы – исследование свойств наночастиц кремния, легированных железом, комплексом аналитических методов и их стабилизация цитрат-анионами для применения в диагностике методом магнитно-резонансной томографии и лечении онкологических заболеваний.Методы. Наночастицы кремния, полученные плазмохимическим методом синтеза, были охарактеризованы лазерно-искровым эмиссионным методом, методом атомной эмиссионной спектроскопии, Фурье-ИК-спектроскопией, рентгеновской фотоэлектронной спектроскопией. Гидродинамический диаметр наночастиц оценивали методом динамического светорассеяния. Исследование токсичности наночастиц проводили с помощью колориметрического МТТ теста на метаболическую активность клеток. В исходное сырье при загрузке добавляли элементарное железо с разным атомным соотношением Fe/Si.Результаты. Было показано, что частица имеет кремниевое ядро с аморфной оксидной оболочкой, представляющей собой оксиды кремния с разной степенью окисления SiO x (0 ≤ x ≤ 2). Содержание железа в образцах составило от 0.8 до 1.8 ат. %. Были получены и охарактеризованы коллоидные растворы наночастиц, стабилизированные цитрат-анионами. Анализ цитотоксичности модифицированных частиц нанокремния с использованием моноклонизированных клеток эритролейкоза человека К562 показал отсутствие токсичности для клеток в культуре при концентрации частиц до 5 мкг/мл.Выводы. Полученные модифицированные частицы не обладают токсичностью, поэтому их можно рекомендовать для использования в in vivo приложениях для тераностик
On the interplay between Babai and Černý’s conjectures
Motivated by the Babai conjecture and the Černý conjecture, we study the reset thresholds of automata with the transition monoid equal to the full monoid of transformations of the state set. For automata with n states in this class, we prove that the reset thresholds are upperbounded by 2n2 -6n + 5 and can attain the value (Formula presented). In addition, we study diameters of the pair digraphs of permutation automata and construct n-state permutation automata with diameter (formula presented). © Springer International Publishing AG 2017
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